“By 2040, only ultra-low carbon vehicles will be permitted on UK roads for non-freight purposes,” the policy document states.

The Lib Dems also want to introduce a system of road pricing in congested areas.

While the Coalition ruled out imposing tolls on the existing road network during this side of the election, no promises have been given for the second half of the decade.

The Lib Dems also want to replace air passenger duty with a “per-plane duty, charged in proportion to the carbon emissions created by that journey”.

As part of the party’s plans to create a “zero-carbon” Britain, the Lib Dems could also embrace nuclear power and shale gas exploration.

The Lib Dems will vote to say that gas fracking should be allowed as long as "regulations controlling pollution and protecting local environmental quality are strictly enforced, planning decisions remain with local authorities and local communities are fully consulted over extraction and fully compensated for all damage to the local landscape".

Fracking, which involves fracturing rocks deep underground with water and chemicals to extract oil and natural gas, has dramatically cut energy bills in the USA.

Ministers are hoping that it could do the same in the UK, particularly in the Home Counties and north west of England, however campaigners and local people are bitterly fighting drilling.

Two areas of Surrey and Sussex are estimated by US authorities to hold 700 million barrels of recoverable shale oil - or more than a year’s supply for Britain.

David Cameron has given his support to shale gas drilling but many Tory voters across the country are opposed to fracking and have vowed to stop drilling in their area.